NASA is developing a new docking system for future missions to the International Space Station and other destinations beyond low Earth orbit. A key component of this system is the seal at the main docking interface on the top of the docking system tunnel. The seal is relatively large with a diameter of approximately 50 in. (127 cm) and is compressed during the docking process to seal the interface between the top of the docking system tunnel and the mating surface on the vehicle to which it is docking. After docking, the seal must exhibit extremely low leak rates to ensure that astronauts have sufficient breathable air for extended missions. When the docking system is not docked, the seal is left uncovered and is exposed to the environment in space including atomic oxygen, ultraviolet radiation, and impacts from micrometeoroids and orbital debris. These conditions degrade the seal material and cause higher than desired leak rates after docking.